Been kind of busy, but thought I should update this thread. I will also update the battery equalization thread as well.

As I started to work on my battery bank to see why two batteries lost fluid pretty quickly, I discovered one dead cell in one of the golf cart batteries (very low reading on the hydrometer).

Apparently that set was dragging down the rest of the bank and the inverter was pumping a lot of current into the battery bank (my crude understanding). In any case, I took that set of batteries out (now have 6 golf cart batteries in bank) and the CO detectors have not shown any issue since then. The battery bank is now acting normal during the float cycle.

Now I have to do some research to see if I can salvage the one battery. I think I will try using a good power supply when I can control the voltage to the proper voltage for a 6V battery and see if working on that specific battery will raise it from the dead.